The use of an electrical junction or outlet box to accommodate electrical cable terminations is well known in the art. These boxes typically house electrical components, such as electrical receptacles, jacks, plugs and other devices. The junction box permits the electrical cables to either pass through or connect to the electrical components housed inside the box. In certain applications, these junction boxes are used in floor installations, and are referred to as floor boxes. Electrical cable distribution takes place beneath the surface of the floor and the junction boxes are designed to be supported within a poured concrete floor. One of the problems in positioning a floor box is that the installer must assure that the top of the floor box is both flush and level with the top of the poured floor in which it is set.
In the prior art, it is known to provide floor boxes which are set in poured concrete floors and then sawed off to accommodate the depth of the poured floor. Examples of these cuttable floor boxes are shown in U.S. Pat. No. 3,343,704 to Terry and U.S. Pat. No. 5,466,886 to Lengyel et al. However, these cuttable floor boxes have certain disadvantages. The cuttable floor boxes typically have an open end and thus require a separate cover to protect the interior of the box from debris and extraneous concrete during pouring of the concrete floor. Furthermore, many of these cuttable floor boxes require complicated assemblies to assure that the terminations housed at the upper end of the box are level with the concrete floor. Additionally, many electrical standards, such as the National Electrical Code (NEC), require floor boxes that accommodate multiple services (e.g., power and communication services) be designed to maintain physical separation between the various services within the box.
In many floor applications, the junction box is positioned on a deck and concrete is poured over the deck to form the floor. The deck typically includes ducts, conduits or corrugations for the passage of the cables under the floor. In these applications, the junction box is positioned on the deck and connected to the duct, conduit or corrugations prior to pouring the concrete. Once the box is properly positioned, the concrete is poured onto the deck and around the junction box to form a concrete floor. In order to accommodate variations in the poured concrete floor thickness, the junction box is typically constructed so that the upper end of the box extends above the level of the poured concrete floor. Once the concrete floor has set, the installer cuts away the portion of the box extending above the surface of the floor so that the top of the box is flush with the surface of the poured concrete floor.
Floor boxes embedded in concrete floors are typically formed of either polyvinyl chloride (PVC) or cast iron. Regardless of the fabrication material, in-floor electrical boxes must often include various internal members. For example, depending on the particular application, an electrical floor box can include upper assemblies, concrete caps, and, in the case of a dual voltage box, voltage dividers. PVC has certain advantages over cast iron boxes, such as ease of manufacture by conventional molding techniques, light weight, nonconductive and low cost. Cast iron electrical boxes have the advantages of greater strength, non-deformability and shaping ability, albeit by secondary manufacturing operations at additional cost.
For many applications, electrical boxes made of either PVC or cast iron are suitable for in-floor installation. PVC boxes are generally preferred because they are less expensive. However, in some cases, local and/or state building codes require electrical boxes installed in concrete floors to be made of a metal, such as cast iron. Thus, it is common for contractors to maintain supplies of both PVC electrical floor boxes and cast iron electrical floor boxes. This adds to their costs and requires additional storage space.
It is, therefore, desirable to provide a PVC floor box for installation in a poured concrete floor which can also be used as part of a cast iron electrical box assembly. It is also desirable to provide a PVC electrical floor box that can be easily and securely installed in a cast iron outer box. Moreover, there is a need for an electrical box with an extension that can be modified for use with concrete floors of different depths.